Traffic or crash barriers keep vehicles within the roadway and prevent vehicles from colliding with dangerous obstacles such as boulders, buildings, walls or drains. Side and centre crash barriers for roads such as motorways are respectively installed on sides and central reserves of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Such crash barriers generally consist of a metal strip, transversally corrugated, supported by vertical columns that are anchored to the ground. These crash barriers are designed to minimize injury to vehicle occupants. However, injuries inevitably occur in collisions with crash barriers.
Early crash barrier designs often paid little attention to the ends or terminals of the barriers, so the barriers either ended abruptly in blunt ends, or sometimes featured some flaring of the edges away from the side of the barrier facing traffic. Vehicles that struck blunt terminals at the incorrect angle could stop too suddenly or have steel rail sections penetrate into the vehicle, resulting in severe injuries or fatalities. As a result, a new style of barrier terminals was developed in the 1960s in which the guardrail was twisted 90 degrees and its end laid down so that it would lie flat at ground level (so-called “turned-down” terminals). While this innovation prevented the rail from penetrating the vehicle, it could also cause a vehicle to vault into the air or cause it to roll over, since the rising and twisting guardrail formed a ramp. These crashes often led to vehicles flying at high speed into the very objects which the crash barriers were supposed to protect them from in the first place.
To address vaulting and rollover crashes, energy or shock-absorbing terminals were developed. These devices are known as end terminals or ‘end treatments’ of crash barriers. The first generation of these terminals in the 1970s were breakaway cable terminals, in which the rail curves back on itself and is connected to a cable that runs between the front and rear posts (which are often breakaway posts). The second generation, in the 1990s and 2000s, featured a large steel impact head that engages the frame or bumper of the vehicle. The impact head is driven back along the guide rail, dissipating the kinetic energy of the vehicle by bending or tearing the steel in the guide rail sections. A guide rail may also be terminated by curving it back to the point that the terminal is unlikely to be hit end-on, or, if possible, by embedding the end in a hillside or cut slope.
End terminals have been tested to comply with the EN1317 standard. EN 1317 is a European standard established in 1998 that defines common testing and certification procedures for road restraint systems. End terminals in the main are formed with corrugated or box beams on posts. Components interact with each other to absorb the impact of vehicles through friction, sliding, or shearing.
Some end terminals involve a tension-based solution rather than compression-based. The energy is absorbed with resistance at the impact head rather than being transferred down the rail as occurs with other systems. Even head on, high angle impacts result in the vehicle being redirected and controlled.
FIGS. 1a to 1b illustrate examples of conventional end terminals for crash barriers. As illustrated in FIGS. 1a and 1b, end terminals are configured to be attached to the terminal portions of crash barriers. FIG. 1c illustrates an example of another type of vehicle restraint device, namely a crash cushion. A crash cushion may comprise a number of water-filled shock absorbers in a grid formation. Crash cushions are standalone shock absorbers that are used to shield concrete barriers or guardrail ends in central reserves or roadsides. Crash cushions can be installed as a permanent or temporary attenuator. Redirective, non-gating crash cushions are road safety devices whose primary function is to protect the end of rigid or semi-rigid barriers or fixed roadside hazards by absorbing the kinetic energy of impact or by allowing controlled redirection of the vehicle. Crash cushion devices are designed to safely decelerate vehicles or redirect errant vehicles away from roadside or median hazards. These devices are typically applied to locations where head-on and angled impacts are likely to occur and it is desirable to have the majority of post impact trajectories on the impact side of the system. In one type of a crash cushion, energy absorbing cartridges can be used to absorb the kinetic energy of an impacting vehicle. The energy absorbing cartridges may be separated by diaphragms and held in place with a framework of corrugated steel rail panels that telescopes rearward during head-on impacts.
An alternative to energy absorbing barrier terminals are impact attenuators. FIG. 1d is an example of an impact attenuator, as disclosed in WO2012074480 (A1). Referring to FIG. 1d, this type of impact attenuator comprises a housing, at least two pins arranged in the housing which are arranged in parallel to each other in the housing, as well as a metallic, elongated draw element, which can be positioned within the housing such that it extends between and in contact with the pins, wherein the pins and the draw element are positioned such that a change of direction appears on the draw element when passing by each pin such that at mutual moving of the draw element and the housing in relation to each other, the movement is decelerated due to deformation of the draw element at passage of each pin. The pins and the draw element are positioned such that the draw element obtains a change of direction of at least 90 degrees when passing at least two of the pins. The impact attenuator comprises a beam and a collision catcher, which is connected to the beam and displaceable along its outer side, wherein one of the energy absorbing device or the draw element is connected to the collision catcher and displaceable together with it, while the other of these is fixedly connected to the ground or a fixed structure such that at a possible collision with the collision catcher, this is decelerated due to the mutual movement between the energy absorbing device and the draw element.
Notwithstanding the above, vehicle restraint devices as described above are distinguished for various negative characteristics, in terms of security, configuration and installation difficulties. Such devices are often bulky, both in a longitudinal and transverse direction. This limits the space that can be utilised for pavements, kerbs and hard shoulders, and also the roadways themselves. Due to the size of such devices, it may not be practically feasible to protect fixed obstacles that remain so utterly exposed to traffic without any protection.
Given the complexity of their design, the above-described vehicle restraint devices are made up of a multitude of components and are all different from each other. This complexity implies a high probability of incorrect installation if not performed by highly skilled and educated personnel. The operating mechanisms of such shock absorbers, based in most cases on reciprocal sliding metal sections, if not installed correctly fail, creating situations of great danger for impactful vehicles.
In view of the above, there is a need for an improved protective device for road crash barriers or any fixed road obstacles.